It is known from U.S. Pat. No. 3,627,739 to polymerize dicyclopentadiene (abbreviated DCPD) to polydicyclopentadiene (poly DCPD) with the aid of a tungsten catalyst. The obtained poly DCPD is rather brittle and has a low Izod impact strength. Efforts have been made to improve this product and European Patent Application No. 84,888 discloses a method to prepare poly DCPD with improved properties. Application 84,888 also discloses a process for the polymerization in bulk of DCPD with the aid of a metathesis catalyst system, comprising e.g. phenol substituted tungsten hexachloride together with an activator, e.g. ethyl aluminum dichloride, and diethyl aluminum chloride or tetrabutyl tin. The application further discloses that the DCPD used should be purified in order to prevent impurities from inhibiting the polymerization. It is stressed that it is often desirable to purify the starting materials even further by treatment with silica.
Applicant has now found a versatile metathesis catalyst system for the polymerization of DCPD in bulk, which is more stable, less sensitive to oxygen and moreover can polymerize DCPD of impure quality.